1. Field of the Invention
This invention relates to control circuits for motors incorporated into reversible power drive for closures such as garage doors and the like and more particularly to a control circuit which is adapted to be operated by push button and/or auxiliary device such as a remote radio receiver transmitter.
2. Prior Art
Radio operated power drive systems for garage doors, security gates and other movable members are in common use and typically comprise a reversible electric motor together with an input signal source such as push button or a radio transmitter-receiver combination for alternately starting the motor in opposite directions of travel. A stop command is typically provided by a device such as a limit switch which responds to the displacement of the movable member at the opposite limit of travel to open circuit the motor.
To insure that the motor is alternately driven in opposite directions for each successively applied input signal it has been common to use a mechanical relay device having a coil and a magnetically displaceable armature element which alternately toggles in a pivot arrangement to make opposite electric circuits to the drive motor. The relay, often termed a "ratchet relay," is a mechanically bi-stable device and has been in use in domestic and commercial garage door operators for many years. It is, however, relatively expensive and requires a momentarily large current surge for proper operation.
U.S. Pat. No. 4,045,715, assigned to the assignee of the present invention, discloses an improved operator for controlling the displacement of garage doors, gates and other similarly displaceable objects wherein the electric mechanically bi-stable relay device of the prior art is replaced with an all electronic bi-stable device commonly known as a solid state flip-flop. It also discloses two switches which are complementally operable by the bi-stable flip-flop to assume open and closed conditions between the line voltage source and the reversible electric motor which form the mode of power source of the operator. In addition the switches are electrically interconnected such that inadvertent closure of both switches effectively disconnects the motor from the power source and prevents improper operation thereof.